Why is it making the same material for two different objects?
Select the first object, and in the material panel, click on the + button (surrounded by a pink frame in the picture) to create a first material (named Material.001) and change its diffuse color.



Select the second object, and in the material panel, press again the + button to create a second material (named Material.002) and change its diffuse color.

Each object should have a different color.